Leptin regulates the proliferation of peripheral regulatory T cells via increasing interleukin-6 in rheumatoid arthritis patients

Abstract

Objective To investigate the influence of Leptin on the proliferation of peripheral blood regulatory T cells in patients with rheumatoid arthritis (RA). Methods Peripheral blood mononuclear cells (PBMCs) were isolated from 6 RA patients. RA PBMCs were stimulated with anti-CD3 (3 μg/ml)/anti-CD28 (2 μg/ml) antibody for 72 h, anti-CD3 (3 μg/ml)/anti-CD28 (2 μg/ml) antibody and Leptin (100 ng/ml) for 72 h, anti-CD3 (3 μg/ml)/anti-CD28 (2 μg/ml) antibody and Leptin (100 ng/ml) and interleukin (IL)-6 receptor antagonist (0.5 μg/ml) for 72 h. Regulatory T cells (Treg) were detected by flow cetometry. IL-6 level and TGF-β levels in the supernatants of RA PBMCs culture were detected by Enzyme linked immunosorbent assay(ELISA). Statistical analysis between the two groups were performed by Wilcoxon Signed Rank Test. Results ① Our results suggested that compared to the control group, RA PBMCs were stimulated by leptin for 72 h had lower percentage of Treg[13.6(11.6, 14.8)% vs 9.8(7.0, 10.0)%, Z=-2.201, P<0.05]; Compared to the control group, the level of IL-6 and TGF-β were elevated when RA PBMCs treated with leptin for 72 h [548.9(508.6, 608.4) ng/L vs 631.8 (538.4, 672.6) ng/L, Z=-1.992, P<0.05; 1175.0 (1 045.4, 1 373.1) ng/L vs 1 580.2 (1 315.3, 1 906.5) ng/L, Z=-2.201, P<0.05]; ② The percentage of Peripheral Treg was increased [9.8(7.0,10.0)% vs 12.3 (9.7, 13.8)%, Z=-1.997, P<0.05] and the level of IL-6 was decreased [631.8(538.4, 672.6) ng/L vs 522.7(339.3, 593.3) ng/L, Z=-2.201, P<0.05] when RA PBMCs was stimulated with IL-6 receptor antagonist and anti-CD3/anti-CD28 antibody and Leptin for 72 h. Conclusion The study has shown that Leptin can down-regulate the percentage of RA peripheral blood Treg via increasing IL-6 secretion. Key words: Leptin; Athritis, rheumatoid; Peripheral blood mononuclear cells; Regulatory T cells; Iinterleukin-6